Retainer for cartridge fuse



Feb. 14, 1967 L. L. GOSNELL 3,304,393

RETAINER FOR CARTRIDGE FUSE Filed Sept. 14, 1965 M/l/ENTOR L. L. GOSNELL QLM 6Q A T TORNE Y United States Patent 3,304,393 RETAINER FOR CARTRIDGE FUSE Lawrence L. Gosneli, Baltimore, Md assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed Sept. 14, 1965, er. No. 487,211 2 Claims. (Cl. 200-129) This invention relates to cap-and-block type cartridge fuse assemblies and specifically to a fuse retainer for holding a cartridge fuse securely within its cap to facilitate installation and removal.

A highly desirable feature of many cap-and-block type fuse holders is that the cartridge fuse remains within the cap during removal to reduce the incidence of dropping the fuse and to avoid the hazards of removal by hand or prong. The conventional method for securing fuse to cap is to provide a light interference fit between the inserted end of the fuse and the inside walls of the cap, as shown, for example, in Patent 2,581,308, issued to H. J. Smith on January 1, 1952. The expedient of an interference fit is inapplicable, however, to the type of holder in which a contact spring is employed in the cap, since a friction fit would negate the springs function and might interfere with a good electrical contact. The same reasons still exist, of course, for securing the fuse to the cap.

Accordingly, a prime object of the invention is to retain readily and inexpensively a cartridge-type fuse within its cap without resort to interference fit.

A further object of the invention is to expedite installation and removal of a cartridge-type fuse by lessening substantially the chances of its being dropped inadevertently in the process.

These and other objects are achieved in accordance With the invention by a thin resilient member comprising an annular segment such as a ring that grips one end of the cartridge fuse and at least one leg with an end nub that engages the cap spring.

In one illustrative embodiment of the invention, the resilient member comprises a ring and an attached leg that is inserted well into the space between the inner Wall of the cap and the spring. An end nu-b on the leg lodges beneath a remote turn of the spring and is held there by the combined effects of its own resiliency and that of the spring. One end of the cartridge fuse is then placed through the ring and into the fuse cap where it makes electrical Contact with the near end of the spring. The leg is sufficiently slim to avoid interfering with the seating of the fuse. The ring retains the fuse in this position with a surprising tenacity that greatly facilitates its installation and removal.

Pursuant to another aspect of the invention, the resiliency of the ring-leg member contributes to the gripping action upon the fuse. Fabricated as a fiat form, the ring portion becomes slightly distended and offset as the fuse is passed through it. An added holding force results since the member tries to assume its normal position and in so doing applies a tensile force to the fuse.

Accordingly, a prime feature of the invention rel-ates to a resilient member having an annular segment and at least one leg, the leg lodging unobtrusively in the spring cap of the fuse holder while the annular segment retains the fuse therein with a positive, enveloping friction grip.

These and other objects and features of the invention will be pointed out with greater particularity in the detailed description of an illustrative embodiment and in the drawing in which:

FIG. 1 is a perspective view of the retaining member;

FIG. 1A is an alternate shape for the retainer in perspective view;

FIG. 1B shows an alternate shape for I the retaining end nub in perspective;

FIG. 2 is a perspective view in partial cutaway showing the member inserted in a fuse cap; and

FIG, 3 shows a cartridge fuse and retaining member installed in a fuse cap.

In FIG. 1 the retaining member shown as 10 comprises a ring 11 at one end and an elongated leg 12 integrally connected with ring 11. At the far end of leg 12 is an end nub 13 which has a blunt point 14 and two shoulders 15 on opposite sides of leg 12. Member 10 is readily fabricated in large numbers from nylon or a similarly resilient material in a molding process. The width 16 of member 11) is relatively thin, on the order of 40 mils, to prevent its interfering with the electrical contact. The neck 17 of member 10 is a resilient juncture of ring 11 and leg 12. Member 10 is fabricated as a fiat form so that when bent at neck 17 a force will be developed that tends to return it to its original shape. An alternative shape for member 10 is illustrated in FIG. 1A wherein the ring 11 has a gap 18 that makes fuse installation easier in some instances. shown in FIG. 1B wherein four shoulders are employed, each designated 15.

In FIG. 2 a fuse cap 20 is shown with a conventional gripping end 21 and use recess 22 in which is seated a contact spring 23. A pair of conventional lock arms 24 extend beyond the outer surface of cap 20 for engagement with corresponding lock grooves 31 in a fuse block 30, shown in FIG. 3.

Member 10 is inserted into cap 20 between inner wall 22 and spring 23, as shown in FIG. 2. Nub 13 and in particular shoulders 15 may be molded of various widths so as to contact a selected one of the several possible turns of spring 23. In FIG. 2, for example, nub 13 is shown reaching beyond one of the more remote spring turns. During insertion, as nub 13 encounters each successive spring turn, the combined action of its own resiliency and that of the contacted spring turn causes shoulders 15 to lodge or snap in place under that turn. This action is the essential means which retains member 10 snugly within cap 20 with a force suflicient to grip a fuse during installation, but which allows member 10 to be removed easily by manual manipulation if desired. An advantage of incorporating only two shoulders 15 on nub 13 is that member 10 is thereby permitted to rotate degrees to remove the shoulders from contact With spring 23 to facilitate easy removal.

When member 10 is in the position shown in FIG. 2, a fuse 40 is placed through the ring and into contact with spring 23, as illustrated in FIG. 3. In this position the fuse is held not only by the frictional action of ring 10 on its surface but also by the light torque imparted to it by the distension of ring 11 with respect to leg 12. When so retained, cap 20 with fuse 40 can be inserted readily into the conventional connector portion 32 of block 30 without risk of dropping the fuse. More importantly, the assembly may be removed from block 30 without leaving the fuse in the connector 32. All of the advantages incident to an interference fit as noted earlier are thereby achieved; and in addition, in accordance with the invention, the cap contact spring is left unimpeded in its prime function.

While the preferred embodiment of the inventive concept has been shown and described, it is to be expressly understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A fuse holder comprising, in combination, a chambered block with contact means therein, a cap disposed within said chambered block and having an interior chamber having an open and a closed end, a coil spring fas- A variation of end nub 13 is tened coaxially at said closed end, a plastic resilient member comprising a loop with a bayonet leg aflixed thereto, said leg being frictionally engaged between the coils of said coil spring and the Wall of said interior chamber and said loop being disposed adjacent said open end to receive and frictionally grip a cartridge fuse, said fuse contacting said coil spring and said chambered block contacting means when said gap is disposed within said block.

2. A fuse holder in accordance with claim 1, wherein said bayonet leg further comprises a winged nub at its far end for engaging one of the coils of said coil spring.

References Cited by the Examiner UNITED STATES PATENTS 4 Allen 2430 Fein 24-30 Schumm 2416 Linton 200129 X BERNARD A. GILHEANY, Primary Examiner.

15 H. B. GILSON, Assistant Examiner. 

1. A FUSE HOLDER COMPRISING, IN COMBINATION, A CHAMBERED BLOCK WITH CONTACT MEANS THEREIN, A CAP DISPOSED WITHIN SAID CHAMBERED BLOCK AND HAVING AN INTERIOR CHAMBER HAVING AN OPEN AND A CLOSED END, A COIL SPRING FASTENED COAXIALLY AT SAID CLOSED END, A PLASTIC RESILIENT MEMBER COMPRISING A LOOP WITH A BAYONET LEG AFFIXED THERETO, SAID LEG BEING FRICTIONALLY ENGAGED BETWEEN THE COILS OF SAID COIL SPRING AND THE WALL OF SAID INTERIOR CHAMBER AND SAID LOOP BEING DISPOSED ADJACENT SAID OPEN END TO RECEIVE AND FRICTIONALLY GRIP A CARTRIDGE FUSE, SAID FUSE CONTACTING SAID COIL SPRING AND SAID CHAMBERED BLOCK CONTACTING MEANS WHEN SAID GAP IS DISPOSED WITHIN SAID BLOCK. 